The compounds of the present invention are antagonists of the VLA-4 integrin (xe2x80x9cvery late antigen-4xe2x80x9d; CD49d/CD29; or xcex14xcex21), the xcex14xcex27 integrin (LPAM-1 and xcex14xcex2p), and/or the xcex19xcex21 integrin, thereby blocking the binding of VLA-4 to its various ligands, such as VCAM-1 and regions of fibronectin, xcex14xcex27 to its various ligands, such as MadCAM-1, VCAM-1 and fibronectin, and/or xcex19xcex21 to its various ligands, such as tenascin, osteopontin and VCAM-1. Thus, these antagonists are useful in inhibiting cell adhesion processes including cell activation, migration, proliferation and differentiation. These antagonists are useful in the treatment, prevention and suppression of diseases mediated by VLA-4-, xcex14xcex27 -, and/or xcex19xcex21 -binding and cell adhesion and activation, such as AIDS-related dementia, allergic conjunctivitis, allergic rhinitis, Alzheimer""s disease, aortic stenosis, asthma, atherosclerosis, autologous bone marrow transplantation, certain types of toxic and immune-based nephritis, contact dermal hypersensitivity, inflammatory bowel disease including ulcerative colitis and Crohn""s disease, inflammatory lung diseases, inflammatory sequelae of viral infections, meningitis, multiple sclerosis, myocarditis, organ transplantation, psoriasis, restenosis, retinitis, rheumatoid arthritis, septic arthritis, stroke, tumor metastasis, type I diabetes, and vascular occlusion following angioplasty.
The present invention relates to susbstituted cyclic amine derivatives which are useful for the inhibition and prevention of leukocyte adhesion and leukocyte adhesion-mediated pathologies. This invention also relates to compositions containing such compounds and methods of treatment using such compounds.
Many physiological processes require that cells come into close contact with other cells and/or extracellular matrix. Such adhesion events may be required for cell activation, migration, proliferation and differentiation. Cell-cell and cell-matrix interactions are mediated through several families of cell adhesion molecules (CAMs) including the selectins, integrins, cadherins and immunoglobulins. CAMs play an essential role in both normal and pathophysiological processes. Therefore, the targetting of specific and relevant CAMs in certain disease conditions without interfering with normal cellular functions is essential for an effective and safe therapeutic agent that inhibits cell-cell and cell-matrix interactions.
The integrin superfamily is made up of structurally and functionally related glycoproteins consisting of xcex1 and xcex2 heterodimeric, transmembrane receptor molecules found in various combinations on nearly every mammalian cell type. (for reviews see: E. C. Butcher, Cell, 67, 1033 (1991); T. A. Springer, Cell, 76, 301 (1994); D. Cox et al., xe2x80x9cThe Pharmacology of the Integrins.xe2x80x9d Medicinal Research Rev. 14, 195 (1994) and V. W. Engleman et al., xe2x80x9cCell Adhesion Integrins as Pharmaceutical Targets.xe2x80x9d in Ann. Repts. in Medicinal Chemistry, Vol. 31, J. A. Bristol, Ed.; Acad. Press, NY, 1996, p. 191).
VLA-4 (xe2x80x9cvery late antigen-4xe2x80x9d; CD49d/CD29; or xcex14xcex21) is an integrin expressed on all leukocytes, except platelets and mature neutrophils, including dendritic cells and macrophage-like cells and is a key mediator of the cell-cell and cell-matrix interactions of these cell types (see M. E. Hemler, xe2x80x9cVLA Proteins in the Integrin Family: Structures, Functions, and Their Role on Leukocytes.xe2x80x9d Ann. Rev. Immunol. 8, 365 (1990)). The ligands for VLA-4 include vascular cell adhesion molecule-1 (VCAM-1) and the CS-1 domain of fibronectin (FN). VCAM-1 is a member of the Ig superfamily and is expressed in vivo on endothelial cells at sites of inflammation. (See R. Lobb et al. xe2x80x9cVascular Cell Adhesion Molecule 1.xe2x80x9d in Cellular and Molecular Mechanisms of Inflammation, C. G. Cochrane and M. A. Gimbrone, Eds.; Acad. Press, San Diego, 1993, p. 151.) VCAM-1 is produced by vascular endothelial cells in response to pro-inflammatory cytokines (See A. J. H. Gearing and W. Newman, xe2x80x9cCirculating adhesion molecules in disease.xe2x80x9d, Immunol. Today, 14, 506 (1993). The CS-1 domain is a 25 amino acid sequence that arises by alternative splicing within a region of fibronectin. (For a review, see R. O. Hynes xe2x80x9cFibronectins.xe2x80x9d, Springer-Velag, NY, 1990.) A role for VLA-4/CS-1 interactions in inflammatory conditions has been proposed (see M. J. Elices, xe2x80x9cThe integrin xcex14xcex21 (VLA-4) as a therapeutic targetxe2x80x9d in Cell Adhesion and Human Disease, Ciba Found. Symp., John Wiley and Sons, NY, 1995, p. 79).
xcex14xcex27 (also referred to as LPAM-1 and xcex14xcex2p) is an integrin expressed on leukocytes and is a key mediator of leukocyte trafficking and homing in the gastrointestinal tract (see C. M. Parker et al., Proc. Natl. Acad. Sci. USA, 89, 1924 (1992)). The ligands for xcex14xcex27 include mucosal addressing cell adhesion molecule-1 (MadCAM-1) and, upon activation of xcex14xcex27, VCAM-1 and fibronectin (Fn). MadCAM-1 is a member of the Ig superfamily and is expressed in vivo on endothelial cells of gut-associated mucosal tissues of the small and large intestine (xe2x80x9cPeyer""s Patchesxe2x80x9d) and lactating mammary glands. (See M. J. Briskin et al., Nature, 363, 461 (1993); A. Hamann et al., J. Immunol., 152, 3282 (1994)). MadCAM-1 can be induced in vitro by proinflammatory stimuli (See E. E. Sikorski et al. J. Immunol., 151, 5239 (1993)). MadCAM-1 is selectively expressed at sites of lymphocyte extravasation and specifically binds to the integrin, xcex14xcex27.
The xcex19xcex21 integrin is found on airway smooth muscle cells, non-intestinal epithelial cells (see Palmeret al., J. Cell Biol., 123, 1289 (1993)), and neutrophils, and, less so, on hepatocytes and basal keratinocytes (see Yokosaki et al., J. Biol. Chem., 269,24144 (1994)). Neutrophils, in particular, are intimately involved in acute inflammatory repsonses. Attenuation of neutrophil involvement and/or activation would have the effect of lessening the inflammation. Thus, inhibition of xcex19xcex21 binding to its respective ligands would be expected to have a positive effect in the treatment of acute inflammatory conditions.
Neutralizing anti-xcex14 antibodies or blocking peptides that inhibit the interaction between VLA-4 and/or xcex14xcex27 and their ligands have proven efficacious both prophylactically and therapeutically in several animal models of disease, including i) experimental allergic encephalomyelitis, a model of neuronal demyelination resembling multiple sclerosis (for example, see T. Yednock et al., xe2x80x9cPrevention of experimental autoimmune encephalomyelitis by antibodies against xcex14xcex21 integrin.xe2x80x9d Nature, 356, 63 (1993) and E. Keszthelyi et al., xe2x80x9cEvidence for a prolonged role of xcex14 integrin throughout active experimental allergic encephalomyelitis.xe2x80x9d Neurology, 47, 1053 (1996)); ii) bronchial hyperresponsiveness in sheep and guinea pigs as models for the various phases of asthma (for example, see W. M. Abraham et al., xe2x80x9cxcex14-Integrins mediate antigen-induced late bronchial responses and prolonged airway hyperresponsiveness in sheep.xe2x80x9d J. Clin. Invest. 93, 776 (1993) and A. A. Y. Milne and P. P. Piper, xe2x80x9cRole of VLA-4 integrin in leucocyte recruitment and bronchial hyperresponsiveness in the gunea-pig.xe2x80x9d Eur. J. Pharmacol., 282, 243 (1995)); iii) adjuvant-induced arthritis in rats as a model of inflammatory arthritis (see C. Barbadillo et al., xe2x80x9cAnti-VLA-4 mAb prevents adjuvant arthritis in Lewis rats.xe2x80x9d Arthr. Rheuma. (Suppl.), 36 95 (1993) and D. Seiffge, xe2x80x9cProtective effects of monoclonal antibody to VLA-4 on leukocyte adhesion and course of disease in adjuvant arthritis in rats.xe2x80x9d J. Rheumatol., 23, 12 (1996)); iv) adoptive autoimmune diabetes in the NOD mouse (see J. L. Baron et al., xe2x80x9cThe pathogenesis of adoptive murine autoimmune diabetes requires an interaction between xcex14-integrins and vascular cell adhesion molecule-1.xe2x80x9d, J. Clin. Invest., 93, 1700 (1994), A. Jakubowski et al., xe2x80x9cVascular cell adhesion molecule-Ig fusion protein selectively targets activated xcex14-integrin receptors in vivo: Inhibition of autoimmune diabetes in an adoptive transfer model in nonobese diabetic mice.xe2x80x9d J. Immunol., 155, 938 (1995), and X. D. Yang et al., xe2x80x9cInvolvement of beta 7 integrin and mucosal addressin cell adhesion molecule-1 (MadCAM-1) in the development of diabetes in nonobese diabetic micexe2x80x9d, Diabetes, 46, 1542 (1997)); v) cardiac allograft survival in mice as a model of organ transplantation (see M. Isobe et al., xe2x80x9cEffect of anti-VCAM-1 and anti-VLA-4 monoclonal antibodies on cardiac allograft survival and response to soluble antigens in mice.xe2x80x9d, Tranplant. Proc., 26, 867 (1994) and S. Molossi et al., xe2x80x9cBlockade of very late antigen-4 integrin binding to fibronectin with connecting segment-1 peptide reduces accelerated coronary arteripathy in rabbit cardiac allografts.xe2x80x9d J. Clin Invest., 95, 2601 (1995)); vi) spontaneous chronic colitis in cotton-top tamarins which resembles human ulcerative colitis, a form of inflammatory bowel disease (see D. K. Podolsky et al., xe2x80x9cAttenuation of colitis in the Cotton-top tamarin by anti-xcex14 integrin monoclonal antibody.xe2x80x9d, J. Clin. Invest., 92, 372 (1993)); vii) contact hypersensitivity models as a model for skin allergic reactions (see T. A. Ferguson and T. S. Kupper, xe2x80x9cAntigen-independent processes in antigen-specific immunity.xe2x80x9d, J. Immunol., 150, 1172 (1993) and P. L. Chisholm et al., xe2x80x9cMonoclonal antibodies to the integrin xcex1-4 subunit inhibit the murine contact hypersensitivity response.xe2x80x9d Eur. J. Immunol., 23, 682 (1993)); viii) acute neurotoxic nephritis (see M. S. Mulligan et al., xe2x80x9cRequirements for leukocyte adhesion molecules in nephrotoxic nephritis.xe2x80x9d, J. Clin. Invest., 91, 577 (1993)); ix) tumor metastasis (for examples, see M. Edward, xe2x80x9cIntegrins and other adhesion molecules involved in melanocytic tumor progression.xe2x80x9d, Curr. Opin. Oncol., 7, 185 (1995)); x) experimental autoimmune thyroiditis (see R. W. McMurray et al., xe2x80x9cThe role of xcex14 integrin and intercellular adhesion molecule-1 (ICAM-1) in murine experimental autoimmune thyroiditis.xe2x80x9d Autoimmunity, 23, 9 (1996); and xi) ischemic tissue damage following arterial occlusion in rats (see F. Squadrito et al., xe2x80x9cLeukocyte integrin very late antigen-4/vascular cell adhesion molecule-1 adhesion pathway in splanchnic artery occlusion shock.xe2x80x9d Eur. J. Pharmacol., 318, 153 (1996; xii) inhibition of TH2 T-cell cytokine production including IL-4 and IL-5 by VLA-4 antibodies which would attenuate allergic responses (J. Clinical Investigation 100, 3083 (1997). The primary mechanism of action of such antibodies appears to be the inhibition of lymphocyte and monocyte interactions with CAMs associated with components of the extracellular matrix, thereby limiting leukocyte migration to extravascular sites of injury or inflammation and/or limiting the priming and/or activation of leukocytes.
There is additional evidence supporting a possible role for VLA-4 interactions in other diseases, including rheumatoid arthritis; various melanomas, carcinomas, and sarcomas, including multiple myeloma; inflammatory lung disorders; acute respiratory distress syndrome (ARDS); pulmonary fibrosis; atherosclerotic plaque formation; restenosis; uveitis; and circulatory shock (for examples, see A. A. Postigo et al., xe2x80x9cThe xcex14xcex21/VCAM-1 adhesion pathway in physiology and disease.xe2x80x9d, Res. Immunol., 144, 723 (1994) and J. -X. Gao and A. C. Issekutz, xe2x80x9cExpression of VCAM-1 and VLA-4 dependent T-lymphocyte adhesion to dermal fibroblasts stimulated with proinflammatory cytokines.xe2x80x9d Immunol. 89, 375 (1996)).
At present, there is a humanized monoclonal antibody (Antegren(copyright), Athena Neurosciences/Elan) against VLA-4 in clinical development for the treatment of multiple sclerosis and Crohn""s disease and a humanized monoclonal antibody (ACT-1(copyright)/LDP-02 Millenium/Genentech) against xcex14xcex27 in clinical development for the treatment of inflammatory bowel disease. Several classes of antagonists of VLA-4 and xcex14xcex27 have been described (D. Y. Jackson et al., xe2x80x9cPotent xcex14xcex21 peptide antagonists as potential anti-inflammatory agentsxe2x80x9d, J. Med. Chem., 40, 3359 (1997); H. N. Shroff et al., xe2x80x9cSmall peptide inhibitors of xcex14xcex27 mediated MadCAM-1 adhesion to lymphocytesxe2x80x9d, Bioorg. Med. Chem. Lett., 6, 2495 (1996); K. C. Lin et al., xe2x80x9cSelective, tight-binding inhibitors of integrin xcex14xcex21 that inhibit allergic airway responsesxe2x80x9d, J. Med. Chem., 42, 920 (1999); S. P. Adams and R. R. Lobb, xe2x80x9cInhibitors of Integrin Alpha 4 Beta 1 (VLA-4).xe2x80x9d in Ann. Repts. in Medicinal Chemistry, Vol. 34, A. M. Doherty, Ed.; Acad. Press, NY, 1999, p. 179; U.S. Pat. No. 5,510,332, WO97/03094, WO97/02289, WO96/40781, WO96/22966, WO96/20216, WO96/01644, WO96/06108, WO95/15973, WO99/67230, WO00/00477, and WO00/01690). There are reports of nonpeptidyl inhibitors of the ligands for xcex14-integrins (WO99/36393, WO98/58902, WO96/31206); A. J. Soures et al., Bioorg. Med. Chem. Lett., 8, 2297 (1998). There still remains a need for low molecular weight, specific inhibitors of VLA-4 and xcex14xcex27 -dependent cell adhesion that have improved pharmacokinetic and pharmacodynamic properties such as oral bioavailability and significant duration of action. Such compounds would prove to be useful for the treatment, prevention or suppression of various pathologies mediated by VLA-4 and xcex14xcex27 binding and cell adhesion and activation.
The present invention provides novel compounds of formula I: 
or a pharmaceutically acceptable salt thereof wherein:
X is
1) xe2x80x94Sxe2x80x94,
2) xe2x80x94S(O)mxe2x80x94,
Y is
1) a bond, or
2) xe2x80x94C(R7)(R8)xe2x80x94
m is an integer from 1 to 2;
n is an integer from 1 to 10;
p is a number chosen from 0, 1, 2, or 3;
R1 is
1) hydrogen, provided X is S,
2) C1-10alkyl,
3) C2-10alkenyl,
4) C2-10alkynyl,
5) Cy, or
9) xe2x80x94NRdRe,
wherein alkyl, alkenyl and alkynyl are optionally substituted with one to four substituents selected from Ra, and Cy is optionally substituted with one to four substituents independently selected from Rb;
R2 is
1) hydrogen,
2) C1-10alkyl,
3) C2-10alkenyl, and
4) C2-10alkynyl,
wherein alkyl, alkenyl and alkynyl are optionally substituted with one to four substituents independently selected from Ra;
R3 is
1) C1-10alkyl,
2) Ar1,
3) Ar1xe2x80x94C1-10alkyl,
4) Ar1xe2x80x94Ar2,
5) Ar1xe2x80x94Ar2xe2x80x94C1-10alkyl,
wherein the alkyl group is optionally substituted with one to four substituents selected from Ra, and Ar1 and Ar2 are optionally substituted with one to four substituents independently selected from Rb,
R4 is
1) hydrogen,
2) C1-10alkyl,
3) C2-10alkenyl,
4) C2-10alkynyl,
wherein alkyl, alkenyl and alkynyl are optionally substituted with one to four substituents independently selected from Ra;
R5 is
1) hydroxy,
2) C1-10alkoxy,
3) C2-10alkenyloxy,
4) C2-10alkynyloxy,
5) Cyxe2x80x94Oxe2x80x94,
6) Cyxe2x80x94C1-10alkoxy,
7) amino,
8) C1-10alkylamino,
9) di(C1-10alkyl)amino,
10) Cyxe2x80x94C1-10alkylamino,
wherein alkyl, alkenyl and alkynyl are optionally substituted with one to four substituents selected from Ra, and Cy is optionally substituted with one to four substituents independently selected from Rb;
R6 is
1) hydrogen,
2) C1-10 alkyl,
3) C2-10 alkenyl,
4) C2-10 alkynyl,
5) Cy
6) xe2x80x94S(O)mRd,
7) xe2x80x94S(O)mNRdRe,
8) xe2x80x94C(O)Rd,
9) xe2x80x94CO2Rd,
10) xe2x80x94CO2(CRfRg)nCONRdRe, or
11) xe2x80x94C(O)NRdRe,
wherein alkyl, alkenyl and alkynyl are optionally substituted with one to four substituents independently selected from Ra, and Cy is optionally substituted with one to four substituents indepdently selected from Rb; or
R6 and an Rh attached to the carbon atom adjacent to the ring nitrogen together complete a 4-8 membered ring optionally containing one other heteroatom chosen from nitrogen, oxygen and sulfur;
R7 is
1) hydrogen,
2) C1-10 alkyl,
3) C2-10 alkenyl,
4) C2-10 alkynyl,
5) Ar1,
6) Ar1xe2x80x94C1-10alkyl,
7) xe2x80x94ORd,
8) xe2x80x94O(cRfRg)nNRdRe,
9) xe2x80x94OC(O)Rd,
10) xe2x80x94OC(O)NRdRe,
11) halogen,
12) xe2x80x94SRd,
13) xe2x80x94S(O)mRd,
14) xe2x80x94S(O)2ORd,
15) xe2x80x94S(O)mNRdRe,
16) xe2x80x94NO2,
17) xe2x80x94NRdRe,
18) xe2x80x94NRdC(O)Re,
19) xe2x80x94NRdS(O)mRe,
20) xe2x80x94NRdC(O)ORe, or
21) xe2x80x94NRdC(O)NRdRe,
wherein alkyl, alkenyl, alkynyl and Ar1 are optionally substituted with one to four substituents selected from a group independently selected from Rc;
R8 is
1) hydrogen,
2) C1-10 alkyl,
3) C2-10 alkenyl,
4) C2-10 alkynyl,
5) Cy, or
6) Ar1xe2x80x94C1-10alkyl,
wherein alkyl, alkenyl, alkynyl, Cy and Ar1 are optionally substituted with one to four substituents selected from a group independently selected from Rc;
Ra is
1) halogen,
2) xe2x80x94ORd,
3) xe2x80x94OC(O)Rd,
4) xe2x80x94OC(O)NRdRe,
5) xe2x80x94O(CRfRg)nNRdRe,
6) xe2x80x94SRd,
7) xe2x80x94S(O)mRd,
8) xe2x80x94S(O)2ORd,
9) xe2x80x94S(O)mNRdRe,
10) xe2x80x94NRdRe,
11) xe2x80x94NRdC(O)Re,
12) xe2x80x94NRdC(O)ORe,
13) xe2x80x94NRdC(O)NRdRe,
14) xe2x80x94C(O)Rd,
15) xe2x80x94CO2Rd,
16) xe2x80x94C(O)NRdRe,
17) xe2x80x94CO2(CRfRg)nCONRdRe,
18) xe2x80x94CN,
19) xe2x80x94CRd(Nxe2x80x94ORe),
20) xe2x80x94NO2,
21) CF3,
22) xe2x80x94OCF3, or
23) Cy optionally substituted with one to four substituents independently selected from Rc;
Rb is
1) a group selected from Ra,
2) C1-10 alkyl,
3) C2-10 alkenyl,
4) C2-10 alkynyl, or
8) Ar1xe2x80x94C1-10alkyl,
wherein alkyl, alkenyl, alkynyl and Ar1 are optionally substituted with one to four substituents selected from a group independently selected from Rc;
Rc is
1) halogen,
2) amino,
3) C1-4alkylamino,
4) di(C1-4alkyl)amino
5) carboxy,
6) cyano,
7) C1-4alkyl,
8) arylC1-4alkyl,
9) Ar1,
10) hydroxy,
11) C1-4alkoxy,
12) aryloxy, or
13) CF3;
Rd and Re are independently selected from hydrogen, C1-10alkyl, C2-10alkenyl, C2-10alkynyl, Cy and Cy C1-10alkyl, wherein alkyl, alkenyl, alkynyl and Cy are optionally substituted with one to four substituents independently selected from Rc; or
Rd and Re together with the atoms to which they are attached form a heterocyclic ring of 4 to 7 members containing 0-2 additional heteroatoms independently selected from oxygen, sulfur and nitrogen;
Rf and Rg are independently selected from hydrogen, C1-10alkyl, Cy and Cyxe2x80x94C1-10alkyl; or
Rf and Rg together with the carbon to which they are attached form a ring of 4 to 7 members containing 0-2 heteroatoms independently selected from oxygen, sulfur and nitrogen;
Rh is
1) a group selected from Ra,
2) C1-10 alkyl,
3) C2-10 alkenyl,
4) C2-10 alkynyl,
5) Cy,
6) oxo,
wherein alkyl, alkenyl, alkynyl, and Cy are optionally substituted with one to four substituents selected from a group independently selected from Rc; or
two Rh groups attached to adjacent ring atoms together complete 4-8 membered aromatic or non-aromatic ring containing 0-2 heteroatom selected from oxygen, sulfur and nitrogen; or
two Rh groups attached to the same ring atom together complete a 4-8 membered ring containing 0-2 heteroatom selected from oxygen, sulfur and nitrogen;
with the proviso that when Rh is chosen from
1) xe2x80x94ORd,
2) xe2x80x94OC(O)Rd,
3) xe2x80x94OC(O)NRdRe,
4) xe2x80x94O(CRfRg)nNRdRe,
5) xe2x80x94SRd,
6) xe2x80x94S(O)mRd,
7) xe2x80x94S(O)2ORd,
8) xe2x80x94S(O)mNRdRe,
9) xe2x80x94NRdRe,
10) xe2x80x94NRdC(O)Re,
11) xe2x80x94NRdC(O)ORe,
12) xe2x80x94NRdC(O)NRdRe, or
13) xe2x80x94NO2,
14) halogen,
15) xe2x80x94CN, and
16) xe2x80x94CRd(Nxe2x80x94ORe),
xe2x80x83it is not attached to an atom adjacent to the ring nitrogen;
Cy is cycloalkyl, heterocyclyl, aryl or heteroaryl;
Ar1 and Ar2 are independently selected from aryl and heteroaryl.
In one subset of compounds of formula I, X is S or SO2. In one preferred embodiment X is S. In another preferred embodiment X is SO2.
In another subset of compounds of formula I, Y is a bond.
In another subset of compounds of formula I, R1 is C1-10 alkyl optionally substituted with one to four substituents selected from Ra, or Cy optionally substituted with one to four substituents selected from Rb. In one preferred embodiment R1 is C1-5alkyl optionally substituted with one to two substituents selected from Ra; more prefereably R1 is C1-5alkyl optionally substituted with a group selected from NRdRe, NO2, phenyl, hydroxy and 1-imidazolyl. In another preferred embodiment R1 is aryl or heteroaryl each optionally substituted with one to two substituents selected from Rb; more preferably R1 is phenyl optionally substituted with one or two substituents selected from halogen and NRdRe. Examples of R1 include phenyl, 4-bromophenyl, 3-bromophenyl, 2-bromophenyl, 4-(benzylamino)phenyl, 3-(benzylamino)phenyl, 4-(1-pyrrolidinyl)phenyl, 3-(1-pyrrolidinyl)-phenyl, benzyl, 1-methyl-4-imidazolyl, 1-methyl-5-imidazolyl, methyl, 2-(1-piperidinyl)ethyl, 2-(4-morpholinyl)ethyl, 2-(3-(dimethylamino)propylamino)ethyl, 3-nitropropyl, 2-(1-imidazolyl)ethyl, and 2-hydroxyethyl.
In another subset of compounds of formula I, R2 and R4 are each hydrogen.
In another subset of compounds of formula I, R3 is Ar1xe2x80x94C1-3alkyl or Ar1xe2x80x94Ar2xe2x80x94C1-3alkyl; more preferably, R3 is Ar1xe2x80x94CH2 or Ar1xe2x80x94Ar2xe2x80x94CH2; Ar1 and Ar2 are each optionally substituted with one to four groups independently selected from Rb. Even more preferred R3 is optionally substituted benzyl or optionally substituted Ar2-benzyl, where Ar2 is optionally substituted phenyl, or optionally substituted 5- or 6-membered heteroaryl. Even more preferred R3 is benzyl, benzyl substituted with a group selected from hydroxy, C1-5alkoxy, NHC(O)Re, OC(O)NRdRe, and C(O)NRdRe, or 4-(Ar2)-benzyl wherein Ar2 is phenyl substituted with one to two groups selected from C1-5alkyl, hydroxy, C1-5alkoxy and NRdRe, or Ar2 is 2-ethyl-4-thiazolyl. Most preferably, R4 is 4-(2xe2x80x2,6xe2x80x2-dimethoxyphenyl)benzyl. Examples of R3 inlude 4-(2xe2x80x2-methoxyphenyl)benzyl, 4-(2xe2x80x2,6xe2x80x2-dimethoxyphenyl)benzyl, 4-(2xe2x80x2-cyanophenyl)benzyl, 4-(2xe2x80x2-cyano-6xe2x80x2-methoxyphenyl)benzyl, 4-(2xe2x80x2-hydroxy-6xe2x80x2-methoxyphenyl)benzyl, 4-(2xe2x80x2-dimethylamino-6xe2x80x2-methoxyphenyl)benzyl, 4-(2xe2x80x2-ethyl-6xe2x80x2-methoxyphenyl)benzyl,benzyl, 4-hydroxybenzyl, 4-(2,6-dichlorobenzoylamino)benzyl, 4-(1-pyrrolidincarbonyloxy)benzyl, 4-(1-piperazinecarbonyl)benzyl, 4-(2-ethyl-4-thiazolyl)benzyl, 2-hydroxy-4-(2xe2x80x2,6xe2x80x2-dimethoxyphenyl)benzyl and 2-nitro-4-(2xe2x80x2,6xe2x80x2-dimethoxyphenyl)benzyl.
In another subset of compounds of formula I, R5 is OH.
In another subset of compounds of formula I, R6 is H or C1-5alkyl. Preferably R6 is hydrogen.
A preferred embodiment of formula I provides compounds of formula Ia: 
wherein
X is
1) S or
2) SO2;
R1 is
1) C1-5alkyl optionally substituted with one to two substituents selected from Ra;
2) aryl or heteroaryl each optionally substituted with one to two substituents selected from Rb;
R3 is
1) Ar1xe2x80x94C1-3alkyl, or
2) Ar1xe2x80x94Ar2xe2x80x94C1-3alkyl;
R6 is
1) hydrogen or
2) C1-5alkyl;
Ra, Rb, Ar1 and Ar2 are as defined above for formula I.
A more preferred embodiment of formula I provides compounds of formula Ib: 
wherein
X is
1) S or
2) SO2;
R1 is
1) C1-5alkyl optionally substituted with a group selected from NRdRe, NO2, phenyl, hydroxy and 1-imidazolyl;
2) phenyl optionally substituted with one or two substituents selected from halogen and NRdRe;
R6 is
1) hydrogen or
2) C1-5alkyl;
Rb1 and Rb2 are independently selected from
1) hydrogen,
2) C1-5alkyl,
3) hydroxy,
4) C1-5alkoxy and
5) NRdRe;
Rd and Re are as defined above for formula I.
A more preferred embodiment of formula I provides compounds of formula Ic: 
wherein
X is
1) S or
2) SO2;
R1 is
1) C1-5alkyl optionally substituted with a group selected from NRdRe, NO2, phenyl, hydroxy and 1-imidazolyl;
2) phenyl optionally substituted with one or two substituents selected from halogen and NRdRe;
R6 is
1) hydrogen or
2) C1-5alkyl;
Rb3 is
1) hydrogen,
2) hydroxy,
3) C1-5alkoxy,
4) NHC(O)Re,
5) OC(O)NRdRe, or
6) C(O)NRdRe,
Rd and Re are as defined above for formula I.
Examples of compounds of the present invention include:
xe2x80x9cAlkylxe2x80x9d, as well as other groups having the prefix xe2x80x9calkxe2x80x9d, such as alkoxy, alkanoyl, means carbon chains which may be linear or branched or combinations thereof. Examples of alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, sec- and tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl, and the like.
xe2x80x9cAlkenylxe2x80x9d means carbon chains which contain at least one carbon-carbon double bond, and which may be linear or branched or combinations thereof. Examples of alkenyl include vinyl, allyl, isopropenyl, pentenyl, hexenyl, heptenyl, 1-propenyl, 2-butenyl, 2-methyl-2-butenyl, and the like.
xe2x80x9cAlkynylxe2x80x9d means carbon chains which contain at least one carbon-carbon triple bond, and which may be linear or branched or combinations thereof. Examples of alkynyl include ethynyl, propargyl, 3-methyl-1-pentynyl, 2-heptynyl and the like.
xe2x80x9cCycloalkylxe2x80x9d means mono- or bicyclic saturated carbocyclic rings, each of which having from 3 to 10 carbon atoms. The term also includes monocyclic rings fused to an aryl group in which the point of attachment is on the non-aromatic portion. Examples of cycloalkyl include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, tetrahydronaphthyl, decahydronaphthyl, indanyl, and the like.
xe2x80x9cArylxe2x80x9d means mono- or bicyclic aromatic rings containing only carbon atoms. The term also includes aryl group fused to a monocyclic cycloalkyl or monocyclic heterocyclyl group in which the point of attachment is on the aromatic portion. Examples of aryl include phenyl, naphthyl, indanyl, indenyl, tetrahydronaphthyl, 2,3-dihydrobenzofuranyl, dihydrobenzopyranyl, 1,4-benzodioxanyl, and the like.
xe2x80x9cHeteroarylxe2x80x9d means a mono- or bicyclic aromatic ring containing at least one heteroatom selected from N, O and S, with each ring containing 5 to 6 atoms. Examples of heteroaryl include pyrrolyl, isoxazolyl, isothiazolyl, pyrazolyl, pyridyl, oxazolyl, oxadiazolyl, thiadiazolyl, thiazolyl, imidazolyl, triazolyl, tetrazolyl, furanyl, triazinyl, thienyl, pyrimidyl, pyridazinyl, pyrazinyl, benzoxazolyl, benzothiazolyl, benzimidazolyl, benzofuranyl, benzothiophenyl, furo(2,3-b)pyridyl, quinolyl, indolyl, isoquinolyl, and the like.
xe2x80x9cHeterocyclylxe2x80x9d means mono- or bicyclic saturated rings containing at least one heteroatom selected from N, S and O, each of said ring having from 3 to 10 atoms in which the point of attachment may be carbon or nitrogen. The term also includes monocyclic heterocycle fused to an aryl or heteroaryl group in which the point of attachment is on the non-aromatic portion. Examples of xe2x80x9cheterocyclylxe2x80x9d include pyrrolidinyl, piperidinyl, piperazinyl, imidazolidinyl, 2,3-dihydrofuro(2,3-b)pyridyl, benzoxazinyl, tetrahydrohydroquinolinyl, tetrahydroisoquinolinyl, dihydroindolyl, and the like. The term also includes partially unsaturated monocyclic rings that are not aromatic, such as 2- or 4-pyridones attached through the nitrogen or N-substituted-(1H,3H)-pyrimidine-2,4-diones (N-substituted uracils).
xe2x80x9cHalogenxe2x80x9d includes fluorine, chlorine, bromine and iodine.
Optical Isomersxe2x80x94Diastereomersxe2x80x94Geometric Isomersxe2x80x94Tautomers
Compounds of Formula I contain one or more asymmetric centers and can thus occur as racemates and racemic mixtures, single enantiomers, diastereomeric mixtures and individual diastereomers. The present invention is meant to comprehend all such isomeric forms of the compounds of Formula I.
Some of the compounds described herein contain olefinic double bonds, and unless specified otherwise, are meant to include both E and Z geometric isomers.
Some of the compounds described herein may exist with different points of attachment of hydrogen, referred to as tautomers. Such an example may be a ketone and its enol form known as keto-enol tautomers. The individual tautomers as well as mixture thereof are encompassed with compounds of Formula I.
Compounds of the Formula I may be separated into diastereoisomeric pairs of enantiomers by, for example, fractional crystallization from a suitable solvent, for example methanol or ethyl acetate or a mixture thereof. The pair of enantiomers thus obtained may be separated into individual stereoisomers by conventional means, for example by the use of an optically active acid as a resolving agent.
Alternatively, any enantiomer of a compound of the general Formula I or Ia may be obtained by stereospecific synthesis using optically pure starting materials or reagents of known configuration.
Salts
The term xe2x80x9cpharmaceutically acceptable saltsxe2x80x9d refers to salts prepared from pharmaceutically acceptable non-toxic bases or acids including inorganic or organic bases and inorganic or organic acids. Salts derived from inorganic bases include aluminum, ammonium, calcium, copper, ferric, ferrous, lithium, magnesium, manganic salts, manganous, potassium, sodium, zinc, and the like. Particularly preferred are the ammonium, calcium, magnesium, potassium, and sodium salts. Salts derived from pharmaceutically acceptable organic non-toxic bases include salts of primary, secondary, and tertiary amines, substituted amines including naturally occurring substituted amines, cyclic amines, and basic ion exchange resins, such as arginine, betaine, caffeine, choline, N,Nxe2x80x2-dibenzylethylenediamine, diethylamine, 2-diethylaminoethanol, 2-dimethylaminoethanol, ethanolamine, ethylenediamine, N-ethyl-morpholine, N-ethylpiperidine, glucamine, glucosamine, histidine, hydrabamine, isopropylamine, lysine, methylglucamine, morpholine, piperazine, piperidine, polyamine resins, procaine, purines, theobromine, triethylamine, trimethylamine, tripropylamine, tromethamine, and the like.
When the compound of the present invention is basic, salts may be prepared from pharmaceutically acceptable non-toxic acids, including inorganic and organic acids. Such acids include acetic, benzenesulfonic, benzoic, camphorsulfonic, citric, ethanesulfonic, fumaric, gluconic, glutamic, hydrobromic, hydrochloric, isethionic, lactic, maleic, malic, mandelic, methanesulfonic, mucic, nitric, pamoic, pantothenic, phosphoric, succinic, sulfuric, tartaric, p-toluenesulfonic acid, and the like. Particularly preferred are citric, hydrobromic, hydrochloric, maleic, phosphoric, sulfuric, and tartaric acids.
It will be understood that, as used herein, references to the compounds of Formula I are meant to also include the pharmaceutically acceptable salts.
Utilities
The ability of the compounds of Formula I to antagonize the actions of VLA-4 and/or xcex14xcex27 integrin makes them useful for preventing or reversing the symptoms, disorders or diseases induced by the binding of VLA-4 and or xcex14xcex27 to their various respective ligands. Thus, these antagonists will inhibit cell adhesion processes including cell activation, migration, proliferation and differentiation. Accordingly, another aspect of the present invention provides a method for the treatment (including prevention, alleviation, amelioration or suppression) of diseases or disorders or symptoms mediated by VLA-4 and/or xcex14xcex27 binding and cell adhesion and activation, which comprises administering to a mammal an effective amount of a compound of Formula I. Such diseases, disorders, conditions or symptoms are for example (1) multiple sclerosis, (2) asthma, (3) allergic rhinitis, (4) allergic conjunctivitis, (5) inflammatory lung diseases, (6) rheumatoid arthritis, (7) septic arthritis, (8) type I diabetes, (9) organ transplantation rejection, (10) restenosis, (11) autologous bone marrow transplantation, (12) inflammatory sequelae of viral infections, (13) myocarditis, (14) inflammatory bowel disease including ulcerative colitis and Crohn""s disease, (15) certain types of toxic and immune-based nephritis, (16) contact dermal hypersensitivity, (17) psoriasis, (18) tumor metastasis, and (19) atherosclerosis.
Dose Ranges
The magnitude of prophylactic or therapeutic dose of a compound of Formula I will, of course, vary with the nature of the severity of the condition to be treated and with the particular compound of Formula I and its route of administration. It will also vary according to the age, weight and response of the individual patient. In general, the daily dose range lie within the range of from about 0.001 mg to about 100 mg per kg body weight of a mammal, preferably 0.01 mg to about 50 mg per kg, and most preferably 0.1 to 10 mg per kg, in single or divided doses. On the other hand, it may be necessary to use dosages outside these limits in some cases.
For use where a composition for intravenous administration is employed, a suitable dosage range is from about 0.001 mg to about 25 mg (preferably from 0.01 mg to about 1 mg) of a compound of Formula I per kg of body weight per day and for cytoprotective use from about 0.1 mg to about 100 mg (preferably from about 1 mg to about 100 mg and more preferably from about 1 mg to about 10 mg) of a compound of Formula I per kg of body weight per day.
In the case where an oral composition is employed, a suitable dosage range is, e.g. from about 0.01 mg to about 100 mg of a compound of Formula I per kg of body weight per day, preferably from about 0.1 mg to about 10 mg per kg and for cytoprotective use from 0.1 mg to about 100 mg (preferably from about 1 mg to about 100 mg and more preferably from about 10 mg to about 100 mg) of a compound of Formula I per kg of body weight per day.
For the treatment of diseases of the eye, ophthalmic preparations for ocular administration comprising 0.001-1% by weight solutions or suspensions of the compounds of Formula I in an acceptable ophthalmic formulation may be used.
Pharmaceutical Compositions
Another aspect of the present invention provides pharmaceutical compositions which comprises a compound of Formula I and a pharmaceutically acceptable carrier. The term xe2x80x9ccompositionxe2x80x9d, as in pharmaceutical composition, is intended to encompass a product comprising the active ingredient(s), and the inert ingredient(s) (pharmaceutically acceptable excipients) that make up the carrier, as well as any product which results, directly or indirectly, from combination, complexation or aggregation of any two or more of the ingredients, or from dissociation of one or more of the ingredients, or from other types of reactions or interactions of one or more of the ingredients. Accordingly, the pharmaceutical compositions of the present invention encompass any composition made by admixing a compound of Formula I, additional active ingredient(s), and pharmaceutically acceptable excipients.
Any suitable route of administration may be employed for providing a mammal, especially a human with an effective dosage of a compound of the present invention. For example, oral, rectal, topical, parenteral, ocular, pulmonary, nasal, and the like may be employed. Dosage forms include tablets, troches, dispersions, suspensions, solutions, capsules, creams, ointments, aerosols, and the like.
The pharmaceutical compositions of the present invention comprise a compound of Formula I as an active ingredient or a pharmaceutically acceptable salt thereof, and may also contain a pharmaceutically acceptable carrier and optionally other therapeutic ingredients. The term xe2x80x9cpharmaceutically acceptable saltsxe2x80x9d refers to salts prepared from pharmaceutically acceptable non-toxic bases or acids including inorganic bases or acids and organic bases or acids.
The compositions include compositions suitable for oral, rectal, topical, parenteral (including subcutaneous, intramuscular, and intravenous), ocular (ophthalmic), pulmonary (aerosol inhalation), or nasal administration, although the most suitable route in any given case will depend on the nature and severity of the conditions being treated and on the nature of the active ingredient. They may be conveniently presented in unit dosage form and prepared by any of the methods well-known in the art of pharmacy.
For administration by inhalation, the compounds of the present invention are conveniently delivered in the form of an aerosol spray presentation from pressurized packs or nebulisers. The compounds may also be delivered as powders which may be formulated and the powder composition may be inhaled with the aid of an insufflation powder inhaler device. The preferred delivery systems for inhalation are metered dose inhalation (MDI) aerosol, which may be formulated as a suspension or solution of a compound of Formula I in suitable propellants, such as fluorocarbons or hydrocarbons and dry powder inhalation (DPI) aerosol, which may be formulated as a dry powder of a compound of Formula I with or without additional excipients.
Suitable topical formulations of a compound of formula I include transdermal devices, aerosols, creams, ointments, lotions, dusting powders, and the like.
In practical use, the compounds of Formula I can be combined as the active ingredient in intimate admixture with a pharmaceutical carrier according to conventional pharmaceutical compounding techniques. The carrier may take a wide variety of forms depending on the form of preparation desired for administration, e.g., oral or parenteral (including intravenous). In preparing the compositions for oral dosage form, any of the usual pharmaceutical media may be employed, such as, for example, water, glycols, oils, alcohols, flavoring agents, preservatives, coloring agents and the like in the case of oral liquid preparations, such as, for example, suspensions, elixirs and solutions; or carriers such as starches, sugars, microcrystalline cellulose, diluents, granulating agents, lubricants, binders, disintegrating agents and the like in the case of oral solid preparations such as, for example, powders, capsules and tablets, with the solid oral preparations being preferred over the liquid preparations. Because of their ease of administration, tablets and capsules represent the most advantageous oral dosage unit form in which case solid pharmaceutical carriers are obviously employed. If desired, tablets may be coated by standard aqueous or nonaqueous techniques.
In addition to the common dosage forms set out above, the compounds of Formula I may also be administered by controlled release means and/or delivery devices such as those described in U.S. Pat. Nos. 3,845,770; 3,916,899; 3,536,809; 3,598,123; 3,630,200 and 4,008,719.
Pharmaceutical compositions of the present invention suitable for oral administration may be presented as discrete units such as capsules, cachets or tablets each containing a predetermined amount of the active ingredient, as a powder or granules or as a solution or a suspension in an aqueous liquid, a non-aqueous liquid, an oil-in-water emulsion or a water-in-oil liquid emulsion. Such compositions may be prepared by any of the methods of pharmacy but all methods include the step of bringing into association the active ingredient with the carrier which constitutes one or more necessary ingredients. In general, the compositions are prepared by uniformly and intimately admixing the active ingredient with liquid carriers or finely divided solid carriers or both, and then, if necessary, shaping the product into the desired presentation. For example, a tablet may be prepared by compression or molding, optionally with one or more accessory ingredients. Compressed tablets may be prepared by compressing in a suitable machine, the active ingredient in a free-flowing form such as powder or granules, optionally mixed with a binder, lubricant, inert diluent, surface active or dispersing agent. Molded tablets may be made by molding in a suitable machine, a mixture of the powdered compound moistened with an inert liquid diluent. Desirably, each tablet contains from about 1 mg to about 500 mg of the active ingredient and each cachet or capsule contains from about 1 to about 500 mg of the active ingredient.
The following are examples of representative pharmaceutical dosage forms for the compounds of Formula I:
Combination Therapy
Compounds of Formula I may be used in combination with other drugs that are used in the treatment/prevention/suppression or amelioration of the diseases or conditions for which compounds of Formula I are useful. Such other drugs may be administered, by a route and in an amount commonly used therefor, contemporaneously or sequentially with a compound of Formula I. When a compound of Formula I is used contemporaneously with one or more other drugs, a pharmaceutical composition containing such other drugs in addition to the compound of Formula I is preferred. Accordingly, the pharmaceutical compositions of the present invention include those that also contain one or more other active ingredients, in addition to a compound of Formula I. Examples of other active ingredients that may be combined with a compound of Formula I, either administered separately or in the same pharmaceutical compositions, include, but are not limited to: (a) other VLA-4 antagonists such as those described in U.S. Pat. No. 5,510,332, WO97/03094, WO97/02289, WO96/40781, WO96/22966, WO96/20216, WO96/01644, WO96/06108, WO95/15973 and WO96/31206; (b) steroids such as beclomethasone, methylprednisolone, betamethasone, prednisone, dexamethasone, and hydrocortisone; (c) immunosuppressants such as cyclosporin, tacrolimus, rapamycin and other FK-506 type immunosuppressants; (d) antihistamines (H1-histamine antagonists) such as bromopheniramine, chlorpheniramine, dexchlorpheniramine, triprolidine, clemastine, diphenhydramine, diphenylpyraline, tripelennamine, hydroxyzine, methdilazine, promethazine, trimeprazine, azatadine, cyproheptadine, antazoline, pheniramine pyrilamine, astemizole, terfenadine, loratadine, cetirizine, fexofenadine, descarboethoxyloratadine, and the like; (e) non-steroidal anti-asthmatics such as xcex22-agonists (terbutaline, metaproterenol, fenoterol, isoetharine, albuterol, bitolterol, salmeterol and pirbuterol), theophylline, cromolyn sodium, atropine, ipratropium bromide, leukotriene antagonists (zafirlukast, montelukast, pranlukast, iralukast, pobilukast, SKB-106,203), leukotriene biosynthesis inhibitors (zileuton, BAY-1005); (f) non-steroidal antinflammatory agents (NSAIDs) such as propionic acid derivatives (alminoprofen, benoxaprofen, bucloxic acid, carprofen, fenbufen, fenoprofen, fluprofen, flurbiprofen, ibuprofen, indoprofen, ketoprofen, miroprofen, naproxen, oxaprozin, pirprofen, pranoprofen, suprofen, tiaprofenic acid, and tioxaprofen), acetic acid derivatives (indomethacin, acemetacin, alclofenac, clidanac, diclofenac, fenclofenac, fenclozic acid, fentiazac, furofenac, ibufenac, isoxepac, oxpinac, sulindac, tiopinac, tolmetin, zidometacin, and zomepirac), fenamic acid derivatives (flufenamic acid, meclofenamic acid, mefenamic acid, niflumic acid and tolfenamic acid), biphenylcarboxylic acid derivatives (diflunisal and flufenisal), oxicams (isoxicam, piroxicam, sudoxicam and tenoxican), salicylates (acetyl salicylic acid, sulfasalazine) and the pyrazolones (apazone, bezpiperylon, feprazone, mofebutazone, oxyphenbutazone, phenylbutazone); (g) cyclooxygenase-2 (COX-2) inhibitors such as celecoxib and rofecoxib; (h) inhibitors of phosphodiesterase type IV (PDE-IV) such as Ariflo and roflumilast; (i) antagonists of the chemokine receptors, especially CCR-1, CCR-2, and CCR-3; (j) cholesterol lowering agents such as HMG-CoA reductase inhibitors (lovastatin, simvastatin and pravastatin, fluvastatin, atorvastatin, and other statins), sequestrants (cholestyramine and colestipol), nicotinic acid, fenofibric acid derivatives (gemfibrozil, clofibrat, fenofibrate and benzafibrate), and probucol; (k) anti-diabetic agents such as insulin, sulfonylureas, biguanides (metformin), a-glucosidase inhibitors (acarbose) and glitazones (troglitazone, pioglitazone, englitazone, rosiglitazone, MCC-555, BRL49653 and the like); (l) preparations of interferon beta (interferon beta-1a, interferon beta-1b); (m) anticholinergic agents such as muscarinic antagonists (ipratropium bromide and tiotropium bromide) and selective muscarinic M3 receptor antagonists such as those described in U.S. Pat. No. 5,948,792; (n) other compounds such as 5-aminosalicylic acid and prodrugs thereof, antimetabolites such as azathioprine and 6-mercaptopurine, and cytotoxic cancer chemotherapeutic agents.
The weight ratio of the compound of the Formula I to the second active ingredient may be varied and will depend upon the effective dose of each ingredient. Generally, an effective dose of each will be used. Thus, for example, when a compound of the Formula I is combined with an NSAID the weight ratio of the compound of the Formula I to the NSAID will generally range from about 1000:1 to about 1:1000, preferably about 200:1 to about 1:200. Combinations of a compound of the Formula I and other active ingredients will generally also be within the aforementioned range, but in each case, an effective dose of each active ingredient should be used.
Compounds of the present invention may be prepared by procedures illustrated in the accompanying schemes. In the first method (Scheme 1), a resin-based synthetic strategy is outlined where the resin employed is represented by the ball (∘). An N-FMOC-protected amino acid derivative A (FMOC=fluorenyl-methoxycarbonyl) is loaded onto an appropriate hydroxyl-containing resin (the choice of resin being dependent on type of linker used, in this case Wang resin was utilized) using 1-ethyl-3-(3xe2x80x2-dimethylaminopropyl)carbodiimide (EDC) and 1-hydroxybenzotriazole (HOBt) in a solvent such as methylene chloride (CH2Cl2) and tetrahydrofuran (THF) or dimethylformamide (DMF) to give B. The FMOC protecting group is removed with piperidine in DMF to yield free amine C. A nipecotic acid derivative D is then coupled to the amine using a reagent such as 2-(1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate (HBTu) in the presence of HOBt and diisopropyl ethyl amine (DIEA) or any of the other well known amide coupling reagents under appropriate conditions: EDC, DCC or BOP (benzotriazole-1-yl-oxy-tris-(dimethylamino)-phosphoniumhexafluorophosphate) to give E. The final product is removed from the resin with strong acid (in this instance, trifluoroacetic acid (TFA in the presence of 5% water) to yield compounds of the present invention F. 
In the second method (Scheme 2), standard solution phase synthetic methodology is outlined. Many amino acid derivatives are commercially available as the tert-butyl or methyl esters and may be used directly in the synthesis outlined below. Amino acid tert-butyl esters B may be prepared from amino acids C directly by treament with isobutylene and sulfuric acid in diglyme or dioxane. Alternatively, N-Boc-protected amino acid derivative A (Boc=tert-butyloxycarbonyl) is treated with tert-butyl 2,2,2-trichloroacetimidate in the presence of boron trifluoride etherate (BF3-Et2O) followed by treatment with strong acid (HCl in ethyl acetate or sulfuric acid in tert-butyl acetate) to remove the t-BOC group to yield tert-butyl ester B which is subsequently coupled to carboxylic acid D in the presence of EDC, HOBt, and DIEA in methylene chloride to yield amide E. The ester is then hydrolysed (in the case of tert-butyl ester with 50% TFA in methylene chloride and for the methyl ester by treatment with 1N sodium hydroxide solution in methanol or dioxane) to provide compounds of the present invention F. 
In a third method (Scheme 3), a late stage intermediate aryl bromide or iodide is coupled to an appropriately substituted aryl or heteroaryl boronic acid to give a subset of compounds of the present invention (R3 =biaryl-substituted-alkyl or heteroaryl-aryl-substituted-alkyl, R2 =hydrogen). For example, 4-iodo or 4-bromo-phenyl-derivative A is converted to the tert-butyl ester B by treatment with isobutylene and sulfuric acid. Alternatively the N-Boc-4-iodo- or 4-bromo-phenyl-derivative C is reacted with tert-butyl 2,2,2-trichloroacetimidate in the presence of boron trifluoride etherate in methylene chloride-cyclohexane followed by treatment with strong acid (HCl in ethyl acetate or sulfuric acid in tert-butyl acetate) to remove the t-BOC group to yield tert-butyl ester B which is subsequently coupled with D in the presence of (for example) EDC, HOBt and NMM to yield amide E. Substituted aryl or heteroaryl boronic acids are coupled to E in the presence of a palladium(0) reagent, such as tetrakis(triphenylphosphine)palladium under Suzuki conditions (N. Miyaura et al., Synth. Commun., 1981, 11, 513-519), followed by removal of the tert-butyl ester using a strong acid (TFA) to yield the desired product F. If the aryl or heteroaryl boronic acid is not commercially available, but the corresponding bromide or iodide is, then the bromide or iodide can be converted into the desired boronic acid by treatment with an alkyllithium reagent in tetrahydrofuran at low temperature followed by addition of trimethyl or triisopropyl borate. Hydrolysis to the boronic acid can be effected by treatment of the intermediate with aqueous base and then acid. 
Alternatively, the aryl coupling reaction may be performed by application of Stile-type carbon-carbon bond forming conditions (Scheme 4). (A. M. Echavarren and J. K. Stille, J. Am. Chem. Soc. 1987, 109, 5478-5486). The aryl bromide or iodide intermediate A is converted into its trialkyltin derivative B using hexamethylditin (((CH3)3Sn)2) in the presence of a palladium(0) catalyst and lithium chloride and then reacted with an appropriately substituted aryl or heteroaryl bromide, iodide, or triflate in the presence of a palladium reagent, such as tetrakis(triphenylphosphine)palladium(0) or tris(dibenzylideneacetone)dipalladium(0), in a suitable solvent, such as toluene, dioxane, DMF, or 1-methyl-2-pyrrolidinone, followed by the removal of the tert-butyl ester using strong acid (TFA) to yield the desired product C. Biphenyl amino acids suitable for attachment to resin (Scheme 1, A) may be prepared by this route as well. Superior coupling conversions and rates may be elicited by application of the method of Farina (J. Org. Chem. 5434, 1993) 
Compounds wherein the proximal ring is heteroaryl (G) may be prepared (Scheme 5) in a similar fashion starting from the appropriate heteroaryl bromide or iodide C using Suzuki-type conditions as depicted in Scheme 3 or from the corresponding heteroaryl trimethyltin using Stille-type conditions as depicted in Scheme 4. The requisite heteroaryl halides C may be prepared via conventional electrophilic halogenation of the N-Boc-heteroaryl-alanine tert-butyl ester intermediate B. B may be prepared from the known aliphatic iodo intermediate A in carbon-carbon bond formation using zinc/copper couple and palladium(II) (M. J. Dunn et al., SYNLETT 1993, 499-500). 
3-Substituted nipecotic acid derivatives may be prepared first by treatment of a nipecotic acid ester A with strong base such as sodium hexamethyldisilazide (Na+ ((CH3)3Si)2Nxe2x88x92) or lithium diisopropylamide (LDA) followed by addition of an appropriate thiolating agent to yield B or D (Scheme 6). Deprotection of the ester would follow as described: TFA for a tert-butyl ester or hydroxide treatment for methyl or ethyl ester to yield C. To prepare the sulfone, treatment of C with a peracid would yield E. Alternatively, A could be treated with a sulfonylating agent such as a sulfonylfluoride followed by ester hydrolysis to yield E. 
Abbreviations
Ac2O: acetic anhydride
BF3xe2x80x94Et2O: borontrifluoride etherate
Bn: benzyl
BOC: tert-butyloxycarbonyl
BOCxe2x80x94ON 2-(tert-butoxycarbonyloxyimino)-2-phenylacetonitrile
BOP: benzotriazol-1-yloxy-tris (dimethylamino)-phosphonium hexafluorophosphate
t-Bu3P: tri-tert-butylphosphine
CBZ: benzyloxycarbonyl
CH2Cl2: methylene chloride
CH3CN: acetonitrile
CH3NO2: nitromethane
CsOH: cesium hydroxide
Cy3P: tricyclohexylphosphine
DIBAL-H: diisobutylaluminum hydride
DBU: 1,8-diazobicyclo[5.4.0]undec-7-ene
DCC: dicyclohexylcarbodiimide
DEA: N,N-diisopropylethylamine
DMAP: 4-(dimethylamino)pyridine
DMF: dimethylformamide
DMSO: dimethylsulfoxide
EDC: 1-(ethyl)-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride
Et: ethyl
EtOAC: ethyl acetate
EtOH: ethanol
FMOC: 9-fluorenylmethoxylcarbonyl
H2SO4: sulfuric acid
HATU: O-(7-azabenzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate
HBTU: O-(benzotriazole-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate
HCl: hydrochloric acid
HOAt: 1-hydroxy-7-azabenzotriazole
HOBt: 1-hydroxybenzotriazole
HPLC: high pressure liquid chromatography
K2CO3: potassium carbonate
KF: potassium fluoride
KI: potassium iodide
LDA: lithium diisopropylamide
m-CPBA: meta-chloroperbenzoic acid
Me: methyl
MeOH: methanol
MgSO4: magnesium sulfate
mmol: millimole
MPLC: medium pressure liquid chromatography
MsCl: methanesulfonyl chloride
NaHCO3: sodium bicarbonate
NaOH: sodium hydroxide
NBS: N-bromosuccinimide
Pd2dba3: tris(di benzylideneacetone) dipalladium(0)
Ph: phenyl
Ph3P: triphenylphosphine
PyBOP: (benzotriazol-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate
TBAF: tetrabutylammonium fluoride
TBSCI: tert-butyldimethylsilyl chloride
TEA: triethylamine
TFA: trifluoroacetic acid
THF: tetrahydrofuran
TLC: thin layer chromatography
TMSCHN2: trimethylsilyldiazomethane
Step A
(L)-4-Iodophenylalanine, methyl ester hydrochloride.
Thionyl chloride (3.6 mL, 50 mmol) was slowly added dropwise to a stirred flask containing methanol (6 mL) at 0xc2x0 C. After the addition, solid N-BOC-(L)-4-iodophenylalanine (3.9 gm, 10 mmol) was added followed by more methanol (10 mL). The mixture was refluxed for 1.5 hr and then cooled to room temperature. The solution was taken to dryness by rotoevaporation and ether (20 mL) and heptane (5 mL) were added. The suspension was again taken to dryness by rotoevaporation and used in the subsequent reaction.
Step B
N-BOC-(L)-4-1odophenylalanine, methyl ester.
The product from Step A (10 mmol) was suspended in THF (20 mL) and methylene chloride (10 mL) at room temperature and triethylamine (2.1 mL, 11 mmol) was added. BOC-ON (2.7 gm, 11 mmo) was added and the solution stirred at room temperature for 5.5 hr. The solution was poured into a mixture of water (100 mL) and EtOAc (100 mL) and separated. The aqueous portion was extracted with EtOAc (2xc3x9750 mL). The combined organic extracts were washed successively with 5% citric acid (50 mL), saturated sodium bicarbonate solution (50 mL), and brine (50 mL) and dried over anhydrous magnesium sulfate. The mixture was filtered and concentrated to an oily residue which was dissolved in ether (50 mL) and placed in a freezer overnight. As no crystals precipitated, the solution was azeotroped with hexanes (2xc3x9750 mL) and the residue purified by flash column chromatography on silica gel eluted with 10% EtOAc in hexanes. Concentration of the chromatography fractions yielded N-BOC-(L)-4-iodophenylalanine, methyl ester (3.1 gm).
Step C
N-BOC-(L)-4-(Trimethylstannyl)phenylalanine, methyl ester.
To a degassed solution of N-BOC-(L)-4-iodophenylalanine, methyl ester (3.1 gm, 7.6 mmol), hexamethylditin (2.2 mL, 11.4 mmol), lithium chloride (0.5 gm, 11.4 mmol), and triphenylphosphine (40 mg, 0.2 mmol) in dioxane was added tetrakis(triphenylphosphine)palladium(II) (0.44 gm, 0.4 mmol). The solution was heated to 95xc2x0 C. overnight under a dry nitrogen atmosphere. The solution was cooled to room temperature and diluted with EtOAc (100 mL) and successively washed with saturated sodium bicarbonate solution and saturated brine. The solution was dried over anhydrous magnesium sulfate, filtered, and concentrated with dry silica gel. The dry powder was placed on a silica gel column and the product purifed by flash column chromatography eluted with 10% EtOAc in hexanes to yield N-BOC-(L)-4-(trimethyl-stannyl)phenylalanine, methyl ester (1.5 gm).
Step D
N-BOC-(L)-4-(2xe2x80x2xe2x80x94Cyanophenyl)phenylalanine, methyl ester.
To a degassed solution of N-BOC-(L)-4-(trimethylstannyl)phenylalanine, methyl ester (1.4 gm, 3.2 mmol) and 2-bromobenzonitrile (1.2 gm, 6.3 mmol) in DMF (8 mL) was added bis(triphenylphosphine)palladium(II)chloride (224 mg, 0.32 mmol). The stirred mixture was placed into a preheated oil bath (90xc2x0 C.) and stirred for 3.5 hr. Heating was stopped and the solution allowed to cool. The solvent was removed by rotoevaporation and the residue dissolved in methylene chloride. The product was purifed on silica gel using a Biotage flash column chromatography apparatus eluted with 15% EtOAc in hexanes to yield N-BOC-(L)-4-(2xe2x80x2-cyanophenyl)phenylalanine, methyl ester (0.5 gm).
Step E
(L)-4-(2xe2x80x2-Cyanophenyl)phenylalanine, methyl ester hydrochloride.
Acetyl chloride (2 mL) was slowly added to a suspension of N-BOC-(L)-4-(2xe2x80x2-cyanophenyl)phenylalanine, methyl ester (0.5 gm, 1.3 mmol) in methanol (10 mL). The solution was stirred overnight at room temperature. The solvent was removed by rotoevaporation to yield (L)-4-(2xe2x80x2-cyanophenyl)phenylalanine, methyl ester hydrochloride (0.75 gm).
Step A
N-BOC-(L)-4-lodophenylalanine, tert-butyl ester.
To a suspension of N-BOC-(L)-4-iodophenylalanine (BACHEM, 5.0 gm, 12.8 mmol) in methylene chloride (35 mL) and cyclohexane (70 mL) was added tert-butyl-2,2,2-trichloroacetimidate (2.93 gm, 13.4 mmol) followed by boron trifluoride (0.24 mL). The suspension was stirred at room temperature for 2 hr after which starting material still remained. Additional tert-butyl-2,2,2-trichloroacetimidate (2.93 gm, 13.4 mmol) and boron trifluoride (0.24 mL) were added and the reaction mixture stirred at room temperature for four days. A third addition of tert-butyl-2,2,2-trichloroacetimidate (2.93 gm, 13.4 mmol) and boron trifluoride (0.24 mL) were added and the reaction mixture stirred at room temperature for 3 hr. The mixture was filtered through a Celite filter pad which was subsequently washed with fresh methylene chloride:cyclohexane (1:1, 2xc3x9725 mL). The solvent was removed by rotoevaporation and the residue purified by flash column chromatography on silica gel eluted with 10% ether in hexane to yield N-BOC-(L)-4-iodophenylalanine, tert-butyl ester as a white crystalline solide (3.3 gm).
Step B
(L)-4-(2xe2x80x2-Cyanophenyl)phenylalanine, tert-butyl ester hydrochloride.
N-BOC-(L)-4-iodophenylalanine, tert-butyl ester was converted to the title compound by the procedures described in Reference Example 1, Steps C through E.
Step A
N-(BOC)-(L)-4-(2xe2x80x2-Methoxyphenyl)phenylalanine, tert-butyl ester.
N-BOC-(L)-4-iodophenylalanine, tert-butyl ester (7.97 g (0.018 mol) was dissolved in 2:1 toluene:ethanol (160 mL). To this solution was added 2-methoxyphenylboronic acid (2.99 g, 20 mmol), tetrakistriphenylphosphine palladium(0) (0.69 g, 0.60 mmol) and a 2.0 M aqueous solution of sodium carbonate (22.7 mL, 0.45 mol). The reaction mixture was degassed three times and then heated at 90xc2x0 C. for 90 minutes at which time the reaction mixture turned black. The mixture was diluted with ethyl acetate (300 mL), washed with water (3xc3x97150 mL) and brine (2xc3x97100 mL), and dried over anhydrous MgSO4. The mixture was filtered and concentrated in vacuo. The residue was purified by flash column chromatography on silica gel eluted with 10% EtOAc in hexanes to give 6.89 g (88% yield) of N-(BOC)-(L)-4-(2xe2x80x2-methoxyphenyl)phenylalanine, tert-butyl ester as a white solid.
300 MHz 1H NMR (CDCl3): xcex4 1.45 (s, 18H); 3.10 (d, 2H); 3.80 (s, 3H); 4.5 (dd, 2H); 5.1 bd, 1H); 7.0 (m, 2H); 7.22 (d, 2H); 7.30 (d, 2H); 7.49 (d, 2H); 7.62 (d, 2H).
Step B
(L)-4-(2xe2x80x2-Methoxyphenyl)phenylalanine, tert-butyl ester HCl.
N-(BOC)-(L)-4-(2xe2x80x2-methoxyphenyl)phenylalanine, tert-butyl ester (8.64 g, 20 mmol) was dissolved in tert-butyl acetate (150 mL) and concentrated sulfuric acid (9.8 g, 100 mmol) was added thereto. The reaction mixture was stirred for 3 hours at room temperature and then diluted with ethyl acetate (150 mL). Addition of 1N NaOH was continued until the solution was basic. The aqueous phase was extracted with EtOAc (4xc3x97100 mL) and the combined organic phases were dried over anhydrous MgSO4, filtered and concentrated in vacuo. The residue was dissolved in 100 mL of ether and treated with anhydrous HCl gas with cooling to give a white solid. The solid was recovered by filtration to give 5.8 g of (L)-4-(2xe2x80x2-methoxyphenyl)phenylalanine, tert-butyl ester hydrochloride. 400 MHz 1H-NMR (CD3OD): 1.42 (s, 9H); 3.20 (d, 2H); 3.79 (s, 3H); 4.20 (t, 1H); 7.00 (t, 1H); 7.06 (d, 1H); 7.25 (dd, 1H); 7.32 (m, 3H); 7.50 (d, 2H).
Step A
N-(BOC)-4-[(Trifluoromethylsulfonyl)oxy]-(L)-phenylalanine, tert-butyl ester.
To a solution of of N-(BOC)-(L)-tyrosine, tert-butyl ester (18.5 g, 55 mmol) in 150 mL of dry methylene chloride was added pyridine (17.4 g, 220 mmol) followed at 0xc2x0 C. by the dropwise addition of of neat triflic anhydride (18.6 g,66 mmol). The reaction mixture was stirred at 0xc2x0 C. and monitored by TLC. After 4 hours, the mixture was diluted with 200 mL of methylene chloride, and washed successively with 1N HCl (3xc3x97100 mL), saturated sodium bicarbonate (2xc3x97100 mL) and brine (1xc3x9750 mL). The solution was dried over anhydrous MgSO4, filtered and concentrated in vacuo to give N-(BOC)-4-[(trifluoromethylsulfonyl)oxy]-(L)-phenyl-alanine, tert-butyl ester as an oil which was used without further purification.
Step B
N-(BOC)-(L)-4-[2xe2x80x2,6xe2x80x2-(Dimethoxyphenyl)]phenylalanine, tert-butyl ester, hydrochloride.
N-(BOC)-4-[(trifluoromethylsulfonyl)oxy]-(L)-phenylalanine, tert-butyl ester (Step A) was dissolved in a mixture of 125 mL of toluene and 61 mL of ethanol. To this solution was added 2,6-dimethoxyboronic acid (11.3 g, 62 mmol) and palladium tetrakistriphenylphosphine (2.5 g). The solution was treated with potassium carbonate (18.3 g, 133 mmol) dissolved in 30 mL of water. The mixture was heated to reflux over 4 hours, cooled to room temperature, and then diluted with 200 mL of ethyl acetate. The solution was washed with water (3xc3x9775 mL) and brine (1xc3x9775 mL), dried over anhydrous MgSO4, filtered and concentrated in vacuo. The residue was purified by flash column chromatography on silica gel eluted with a gradient of 5-20% EtOAc in hexanes to provide 14.7 g of N-(BOC)-(L)-4-[2xe2x80x2,6xe2x80x2-(dimethoxyphenyl)]phenylalanine, tert-butyl ester, hydrochloride as a white solid.
Step C
(L)-4-(2xe2x80x2,6xe2x80x2-(Dimethoxyphenyl)-phenylalanine, tert-butyl ester hydrochloride.
N-(BOC)-(L)4-(2xe2x80x2,6xe2x80x2-(dimethoxyphenyl)-phenylalanine, tert-butyl ester, hydrochloride (Step B) was dissolved in 350 mL of tert-butyl acetate at 0xc2x0 C. and was treated with 8.3 mL of concentrated sulfuric acid. The cold bath was removed and after one hour TLC indicated only starting material was present. The reaction mixture was cooled in an ice bath once more and treated with 3.4 mL of concentrated sulfuric acid. The reaction was monitored by TLC. After consumption of the starting material the reaction mixture was diluted with 300 mL of ethyl acetate and was washed with 3xc3x97100 mL of 1N NaOH followed by brine (1xc3x97100 mL). The solution was dried over anhydrous MgSO4, filtered and concentrated in vacuo to provide 8.9 g of (L)-4-[2xe2x80x2,6xe2x80x2-(dimethoxyphenyl)]phenylalanine, tert-butyl ester hydrochloride.
500 MHz 1H NMR (CD3OD): xcex4 1.45 (s, 9H), 3.20 (d, 2H); 3.69 (s, 6H); 4.20 (t, 1H); 6.72 (d, 2H), 7.15 (m. 5H).
Step A
N-(BOC)-(S)-4-Hydroxyphenylglycine.
To a solution of (S)-(4-hydroxyphenyl)glycine (Sigma Chemical, 6.5 g, 39 mmol) in dioxane/water (1:1, 120 mL) was added triethylamine (5.9 g, 8.2 mL, 58 mmol) and [2-(tert-butoxycarbonyloxyimino)-2-phenylacetonitrile] (BOC-ON; 11 g, 45 mmol). After stirring overnight at room temperature, 300 mL of brine was added to the solution and the mixture was extracted with ether (3xc3x97100 mL). The aqueous layer was acidified with HCl (pH=2) and extracted with 3xc3x97100 mL of ethyl acetate. The ethyl acetate layer was dried over anhydrous MgSO4, filtered and the solvent removed under reduced pressure. The residue was purified by flash column chromatography eluted with a gradient of 2-5% methanol in methylene chloride to yiled 12 g of crude N-(BOC)-(S)-4-hydroxyphenylglycine. An impurity was removed following esterification of the product in the next step.
400 MHz 1H NMR (CDCl3): xcex4 1.37 (s, 9H), 5.1 (1H, br s), 6.7 (d, 2H, J=8 Hz), 7.15 (d, 2H, J=8 Hz).
Step B
N-(BOC)-(S)-4-hydroxyphenylglycine, methyl ester.
In a 50 mL round bottomed flask was added a 1:1 mixture of benzene:methanol and N-(BOC)-(S)-4-hydroxyphenylglycine (2.8 g, 11 mmol). The solution was cooled to 0xc2x0 C. and a 2 M solution of trimethylsilyldiazomethane (Aldrich Chemical Co.) in hexane was added with vigorous stirring until a slight yellow color persisted. The solvents were removed under reduced pressure and the crude product was purified by flash column chromatography (20% EtOAc in hexanes) to give N-(BOC)-(S)-4-hydroxyphenylglycine, methyl ester (2.05 g, 7.3 mmol) (66% yield).
300 MHz 1H NMR (CDCl3): xcex4 1.43 (s, 9H), 3.71 (s, 3H), 5.22 (br d, 1H), 5.57 (1H, br d), 5.80 (br s, 1H), (6.7 (d, 2H, J=8 Hz), 7.17 (d, 2H, J=8 Hz).
Step C
N-(BOC)-(S)-4-[(Trifluoromethylsulfonyl)oxy]phenylglycine. methyl ester.
To a 25 mL round bottom flask fitted with a stir bar and septum was added N-(BOC)-(S)-4-hydroxyphenylglycine, methyl ester (1.9 g, 6.8 mmol) and pyridine (2.8 mL, 33 mmol) in 12 mL methylene chloride. The flask was purged with N2, cooled to 0xc2x0 and trifluoromethanesulfonic anhydride (1.38 mL, 7.8 mmol) was added dropwise over several minutes, keeping the temperature at or below 4xc2x0 C. The solution was stirred for 1 h, then at room temperature for 4 h. The mixture was diluted with 20 mL of methylene chloride, washed with 20 mL of 0.5 N NaOH, 1xc3x9720 mL of water and 2xc3x9720 mL of 10% citric acid. The organic layer was dried over anhydrous MgSO4, filtered, and the solvents removed by evaporation in vacuo. The residue was purified by flash column chromatography on silica gel eluted with 25% methylene chloride in hexane to give 2.3 g of N-(BOC)-(S)-4-[(trifluoromethylsulfonyl)oxy]phenylglycine, methyl ester. (81% yield).
300 MHz 1H NMR (CDCl3): xcex4 1.43 (s, 9H), 3.74 (s, 3H), 5.35 (1H, br d), 5.68 (br s, 1H), 7.27 (d, 2H, J=8 Hz), 7.47 (d, 2H, J=8 Hz).
Step D
N-(BOC)-(S)-(4-Biphenyl)glycine.
To a 25 mL round bottom flask fitted with a stir bar and septum was added N-(BOC)-(S)-4-[(trifluoromethylsulfonyl)oxy]phenylglycine, methyl ester (690 mg, 1.67 mmol), anhydrous potassium carbonate (348 mg, 2.6 mmol) and benzene-boronic acid (411 mg, 3.4 mmol) in 15 mL of toluene and 3 mL of ethanol. The mixture was degassed under nitrogen with three freeze-thaw cycles and tetrakis(triphenylphosphine) palladium (94 mg, 0.085 mmol) was added to the reaction mixture and the mixture was heated between 75-90xc2x0 C. for 4 h. The solvent was removed under reduced pressure and the residue purified by flash column chromatography on silica gel eluted with 15% EtOAc in hexane to give 600 mg of N-(BOC)-(S)-(4-biphenyl)glycine, methyl ester.
300 MHz 1H NMR (CDCl3): xcex4 1.44 (s, 9H), 3.75 (s, 3H), 5.37 (1H, br d), 5.62 (br s, 1H), 7.36 (m, 1H), 7.45 (m, 4H), 7.57 (m, 4H).
The ester was hydrolyzed with 1.2 eq of KOH in 10 mL of 4:1 ethanol:water (2 h). The solution was acidified with 2 N HCl (pH=2). Solvent was removed in vacuo and the free acid was extracted with methylene chloride to provide 430 mg of N-(BOC)-(S)-(4-biphenyl)glycine (66% yield).
Step E
3-(BOC)amino-1-diazo-3-(4-biphenyl)propan-2-one.
To a 25 mL round bottom flask fitted with a stir bar and septum was added N-(BOC)-(S)-4-biphenylglycine (430 mg, 1.31 mmol) in 10 mL of 2:1 methylene chloride: ether. The mixture was cooled to 0xc2x0 C. and N-methylmorpholine (159 xcexcl, 1.44 mmol) was added, followed by dropwise addition of isobutyl chloroformate (179 xcexcL, 1.38 mmol). The mixture was stirred for 1 h at 0xc2x0 C., then diazomethane in ether (excess, prepared from Diazald(copyright) by literature procedure) was added dropwise to the reaction mixture. The mixture was stirred for 1 hr then quenched with saturated sodium bicarbonate. The mixture was extracted with ethyl acetate (2xc3x975 mL), washed with brine then dried over anhydrous MgSO4. The mixture was filtered, the solvent removed under reduced pressure and the product isolated by flash column hromatography on silica gel eluted with 15% EtOAc in hexane to give 280 mg (0.78 mmol) of 3-(BOC)amino-1-diazo-3-(4-biphenyl)propan-2-one (58% yield).
300 MHz 1H NMR (CDCl3): xcex4 1.42 (s, 9H), 5.22 (bs, 1H), 5.29 (s, 1H), 5.9 (br s, 1H), 7.35-7.5 (m, 5H), 7.52-7.62 (m, 4H).
Step F
3(R)-Amino-3-(4-biphenyl)propionic acid, methyl ester
To a 25 mL round bottom flask fitted with a stir bar and septum was added 3-(BOC)amino-1-diazo-3-(4-biphenyl)propan-2-one (280 mg, 0.76 mmol), with 5 mL each of methanol and dioxane. The flask was cooled to 0xc2x0 C. and 0.15 eq (34 mg, 0.038 mmol) of silver benzoate in 500 xcexcl of triethylamine was added dropwise to the reaction mixture and the mixture allowed to stir at 25xc2x0 C. for 1 h. The reaction mixture was treated with 10% NH4OH in saturated NH4Cl (10 mL), then extracted with ether (3xc3x9710 mL), and the organic layer dried over anahydrous MgSO4. After removal of solvents by evaporation in vacuo, the reside was purified by flash column chromatography on silica gel, eluted with 15% EtOAc in hexane. The 260 mg of product (98% yield) was dissolved in 10 mL of 1 N HCl in ethyl acetate. After stirring for 2 h at room temperature, 180 mg of 3(R)-amino-(4-biphenyl)propionic acid, methyl ester hydrochloride, was obtained by filitration.
300 MHz 1H NMR (CD3OD): xcex4 2.90 (dd, 1H, J=18 Hz, J=6 Hz), 3.02 (dd, 1H, J=18 Hz, J=6 Hz), 3.66 (s, 3H), 5.9 (br s, 1H), 7.33-7.5 (m, 5H), 7.55-7.6 (m, 4H).
The following 3(R)-amino-propionic acid derivatives were prepared by the procedures described in Refemece Example 5 substituting the appropriate arylboronic acid analog for benzeneboronic acid:
Step A
N-(CBZ)-4-(trifluoromethylsulfonyloxy)-(L)-phenylalanine, tert-butyl ester.
To a solution of 15.15 g (4.1 mmol) N-(CBZ)-(L)-tyrosine, tert-butyl ester in 150 mL of dry methylene chloride at 0xc2x0 C. was added 12.9 g (164 mmol) of pyridine followed by the dropwise addition of 12.68 g (4.5 mmol) of trifluoromethylsulfonyl chloride. The reaction mixture was stirred at room temperature for 4 hours at which time TLC (25% EtOAc in hexanes) indicated complete consumption of starting material. The reaction mixture was shaken with 1N HCl (3xc3x97100 mL), saturated NaHCO3 solution (2xc3x9750 mL), and brine (1xc3x9750 mL). The organic phase was dried over anhydrous MgSO4, filtered and concentrated in vacuo to give N-(CBZ)-4-(trifluoromethylsulfonyloxy)-(L)-phenylalanine, tert-butyl ester.
400 MHz 1H NMR (CDCl3): xcex4 1.39 (s, 9H); 3.10 (d, 2H); 4.52 (m, 1H); 5.10 (dd, 2H); 7.18 and 7.25 (dd, 2H); 7.30 (m, 5H).
Step B
2-Methoxy-6-(methoxymethyloxy)-phenylboronic acid.
To a solution of 12.0 g (100 mmol) of 3-methoxyphenol in 100 mL of methylene chloride at 0xc2x0 C. was added 29.5 g (229 mmol) of diisopropylethylamine followed by dropwise addition of 10 g of chloromethyl methyl ether. The reaction mixture was stirred at room temperature overnight, washed with 1N HCl (3xc3x9775 mL), 1N NaOH (3xc3x9775 mL) and brine and was dried over anhydrous MgSO4. The mixture was filtered and concentrated in vacuo to give 3-methoxymethyloxy-anisole. 6.0 g (36 mmol) of 3-methoxymethyloxy-anisole was dissolved in 100 mL dry THF and was cooled to xe2x88x9278xc2x0 C. To the solution was added dropwise 20 mL (50 mmol) of 2.5M n-butyl lithium in hexanes. The solution was stirred at xe2x88x9278xc2x0 C. for 1 hour, the ice bath was removed and the solution stirred at room temperature for a further 1 hour. The reaction mixture was cooled to xe2x88x9278xc2x0 C. and treated with 5.56 g (54 mmol) of trimethyl orthoborate. The solution was stirred for 1 hour and then allowed to warm to room temperature over 1 hour. The solution was treated with 30 mL of saturated NH4Cl solution and 100 mL of ethyl acetate with stirring. The pH was immediately adjusted to 5.0 by addition of aliquots of 5% citric acid solution. The aqueous phase was promptly extracted with ethyl acetate (3xc3x9750 mL). The combined ethyl acetate phases were extracted with 1N NaOH solution (3xc3x9750 mL). The combined basic extracts were acidified with rapid stirring by dropwise addition of concentrated hydrochloric acid to pH 5.0. The mixture was extracted by ethyl acetate (3xc3x9775 mL). The combined EtOAc phases were dried over anhydrous MgSO4, filtered and concentrated in vacuo to give 2-methoxy-6-(methoxymethyloxy)phenylboronic acid.
Step
C N-(CBZ)-(L)-4-(2xe2x80x2-Methoxy-6xe2x80x2-methoxymethyloxy-phenyl)-phenylalanine, tert-butyl ester.
To a solution of 7.5 g (15 mmol) of N-(CBZ)-4-(trifluoromethylsulfonyloxy)-(L)-phenylalanine, tert-butyl ester in 75 mL of toluene was added 6.35 g (29 mmol) of 2-methoxy-6-(methoxymethyloxy)-phenylboronic acid followed by 25 mL of ethanol, 25 mL of water, 12 g (87 mmol) of potassium carbonate and 1 g of tetrakistriphenylphosphine palladium (0). The reaction mixture was degassed and then heated at 90xc2x0 C. for 8 hours. The mixture was cooled to room temperature and was diluted with 150 mL of ethyl acetate and was washed with water (3xc3x9775 mL). The organic phase was dried over anhdyrous MgSO4, filtered and concentrated in vacuo. The residue was purified by flash column chromatography on silica gel eluted with a gradient of 25-35% EtOAc in hexanes to give N-(CBZ)-(L)-4-[(2xe2x80x2-methoxy-6xe2x80x2-methoxymethyloxy)phenyl]phenylalanine, tert-butyl ester.
1H-NMR (400 MHz, CDCl3): 1.41 (s, 9H); 3.1 and 3.2 (AB ddd, 2h); 3.31 (s, 3H); 3.72 (s, 3H); 4.60 (m, 1H); 5.03 (s, 2H); 5.15 9s, 2H); 5.40 (bd, 1H); 6.70 (d, 1H); 6.89 (d, 1H); 7.20-7.40 (m, 10H).
Step D
N-(CBZ)-(L)-4-[(2xe2x80x2-Methoxy-6xe2x80x2-hydroxy)phenyl]phenylalanine, tert-butyl ester.
N-(CBZ)-(L)-4-[(2xe2x80x2-methoxy-6xe2x80x2-methoxymethyloxy)phenyl]phenylalanine, tert-butyl ester (3.30 g, 6.4 mmol) was dissolved in 25 mL of tert-butyl alcohol. Pyridinium tosylate (320 mg, 1.3 mmol) was added and the mixture was heated at 85xc2x0 C. for 12 hours. The reaction mixture was heated for 12 hours, then concentrated in vacuo. The residue was dissolved in 100 mL of ethyl acetate and washed with 1N HCl (3xc3x9720 mL), saturated sodium bicarbonate (3xc3x9720 mL) and brine (1xc3x9720 mL). The solution was dried over anhydrous MgSO4, filtered and concentrated in vacuo. The residue was purified by flash column chromatography on silica gel eluted with 25% EtOAc in hexanes to give N-(CBZ)-(L)-4-[(2xe2x80x2-methoxy-6xe2x80x2-hydroxy-phenyl]phenylalanine, tert-butyl ester.
1H-NMR (400 MHz, CDCl3) xcex4 1.42 (s, 9H); 3.15 (d, 2H); 3.72 (s, 3H); 4.58 (m, 1h); 5.13 (s, 2H); 5.35 (d, 1H); 6.55 (d, 1H); 6.68 (d, 1H); 7.21 (t, 1H); 7.25-7.40 (9H).
Step E
N-(CBZ)-(L)-4-(2xe2x80x2-methoxy-6xe2x80x2-trifluoromethylsulfonyloxy-phenyl)-phenylalanine, tert-butyl ester.
N-(CBZ)- (L)-4-[(2xe2x80x2-methoxy)-6xe2x80x2-hydroxy)phenyl]phenylalanine, tert-butyl ester (1.51 g, 3.2 mmol) was dissolved in 20 mL of methylene chloride and treated with 0.75 g (9.6 mmol) of pyridine. The solution was cooled to 0xc2x0 C. and treated with 1.01 g (3.6 mmol) trifluoromethylsulfonic acid anhydride. The reaction mixture was stirred at 0xc2x0 C. over three days. The solution was diluted with methylene chloride, washed with 1N HCl (3xc3x9715 mL), sodium bicarbonate solution (2xc3x9715mL) and dried over anhydrous MgSO4, filtered and concentrated in vacuo. The residue was purified by flash column chromatography on silica gel eluted with 20% EtOAc in hexanes to provide N-(CBZ)-(L)-4-[(2xe2x80x2-methoxy-6xe2x80x2-trifluoromethylsulfonyloxy)phenyl]phenylalanine, tert-butyl ester.
-1H-NMR (400 MHz, CDCl3): 1.45 (s, 9H); 3.16 (d, 2H); 3.78 (s, 3H); 4.60 (m, 1H); 5.13 (s, 2H); 5.27 (d, 1H); 6.99 (d, 1H); 7.02 (d, 1H); 7.25 (m, 4H); 7.31-7.40 (m, 6H).
Step F
N-(CBZ)-(L)-4-[(2xe2x80x2-methoxy-6xe2x80x2-cyano)phenyl]phenylalanine, tert-butyl ester.
To a solution of 0.96 g (1.6 mmol) of N-(CBZ)-(L)-4-[(2xe2x80x2-methoxy-6xe2x80x2-trifluomethylsulfonyloxy)phenyl]phenylalanine, tert-butyl ester in 10 mL of DMF was added 0.37 g (3.1 mmol) of zinc cyanide and 92 mg (0.08 mmol) tetrakistriphenyl-phosphine palladium (0). The reaction mixture was degassed and heated at 90xc2x0 C. for 2 hours. The mixture was diluted with 100 mL of ethyl acetate and was washed with 1N HCl (3xc3x9720 mL), saturated sodium bicarbonate solution (2xc3x9725 mL) and was dried over anhydrous MgSO4, filtered and concentrated in vacuo. The residue was purified by flash column chromatography on silica gel eluted with a gradient of 15-30% EtOAc in hexanes to give N-(CBZ)-(L)-4-[(2xe2x80x2-methoxy-6xe2x80x2-cyano)phenyl]phenylalanine, tert-butyl ester as an oil. NMR (400 MHz, CDCl3): 1.40 (s, 9H); 3.25 (m, 2H); 3.79 (s, 3H); 4.60 (m, 1H); 5.15 (s, 2H); 5.38 (d, 1H); 7.19 (d, 1H); 7.28-7.40 (m, 11H).
Step G
(L)-4-[(2xe2x80x2-methoxy-6xe2x80x2-cyano)phenyl]phenylalanine, tert-butyl ester.
A solution of 0.34 g (0.73 mmol) of N-(CBZ)-(L)-4-[(2xe2x80x2-methoxy-6xe2x80x2-cyano)phenyl]phenylalanine, tert-butyl ester in 5 mL of ethanol was treated with 0.043 g (0.7 mmol) of acetic acid and 25 mg of palladium hydroxide. The mixture was stirred under an atmosphere of hydrogen gas and carefully monitored by TLC for consumption of starting material at which time (2 hours) the mixture was filtered through celite and concentrated in vacuo. The residue was dissolved in 20 mL of ethyl acetate and was washed with 1N NaOH solution (3xc3x975 mL) and was dried over anhydrous MgSO4, filtered and concentrated in vacuo to provide (L)-4-[(2xe2x80x2-methoxy-6xe2x80x2-cyano)phenyl]phenylalanine, tert-butyl ester.
1H-NMR (400 MHz, CDCl3): 1.43 (s, 9H); 1.70 (bs, 2H); 2.93 (dd, 1H); 3.09 (dd, 1H); 3.68 (t, 1H); 3.79 (s, 3H); 7.19 (d, 1H); 7.30-7.40 (m, 6H).
Step A
N-(CBZ)-(L)-4-[(2xe2x80x2-methoxy-6xe2x80x2-ethenyl)phenyl]phenylalanine, tert-butyl ester.
To a solution of 0.32 g (0.52 mmol) of N-(CBZ)-(L)-4-[(2xe2x80x2-methoxy-6xe2x80x2-trifluomethylsulfonyloxy)phenyl]phenylalanine, tert-butyl ester (Reference Example 8, Step E) in 5 mL of dry DMF was added 0.33 g (1.05 mmol) vinyl tributyltin, 36 mg (0.05 mmol) bis-triphenylphosphine palladium dichloride, 0.22 g (5.2 mmol) lithium chloride and 0.082 g (0.3 mmol) of triphenyl phosphine. The mixture was degassed and heated at 90xc2x0 C. After 2 hours 330 mg of vinyltributyl tin was added and the solution was heated overnight. The reaction mixture was cooled and then diluted with ethyl acetate (50 mL) and was washed with saturated KF solution (2xc3x9710 mL), water (2xc3x9720 mL) and brine (1xc3x9710 mL) and was dried over anhydrous MgSO4. The mixture was filtered and concentrated in vacuo. The residue was purified by flash column chromatography on silica gel eluted with 15% EtOAc in hexanes to give N-(CBZ)-(L)-4-[(2xe2x80x2-methoxy-6xe2x80x2-ethenyl)phenyl]phenylalanine, tert-butyl ester.
1H-NMR (400 MHz, CDCl3):1.43 (s, 9H); 3.15 (m, 2H); 3.72 (s, 3H); 4.61 (m, 1H); 5.12 (d, 1H); 5.15 (s, 2H); 5.42 (d, 1H); 5.65 (d, 1H); 6.42 (dd, 1H); 6.92 (dd, 1H); 7.18-7.41 (m, 11H).
Step B
(L)-4-[(2xe2x80x2-methoxy-6xe2x80x2-ethyl)phenyl]phenyalanine, tert-butyl ester.
A solution of 71 mg of N-(CBZ)-(L)-4-[(2xe2x80x2-methoxy-6xe2x80x2-ethenyl)-phenyl]phenylalanine, tert-butyl ester in 5 mL of ethanol and several drops of acetic acid was hydrogenolyzed under atmospheric pressure in the presence of 20% Pd(OH)2 overnight. The reaction mixture was filtered through celite and was concentrated in vacuo. The residue was dissolved in EtOAc and was washed with saturated NaHCO3 and dried over anhydrous MgSO4, filtered and concentrated in vacuo to give (L)-4-[(2xe2x80x2-methoxy-6xe2x80x2-ethyl)phenyl]phenyalanine, tert-butyl ester.
1H-NMR (400 MHz, CDCl3): 1.03 (t, 3H); 1.42 (s, 9H); 1.70 (bs, 2H); 2.40 (q, 2H); 2.95 and 3.07 (dAB, 2H); 3.70 (s, 3H); 6.81 (d, 1H); 6.95 (d,1H); 7.18 (d, 1H); 7.28 (d, 4H).
Step A
2-methoxy-6-dimethylamino-phenylboronic acid.
To a solution of 5.3 g (35 mmol) of 3-dimethylamino-anisole in 25 mL of dry THF at xe2x88x9278xc2x0 C. was added 19 mL (47 mmol) of a 2.5M solution of n-butyl lithium in hexanes. The reaction mixture was stirred for 1 hour before removing the ice bath and warming to room temperature for 90 minutes. The solution was cooled to xe2x88x9278xc2x0 C., treated with 8.75 g (84 mmol) of trimethyl orthoborate, and then stirred for one hour before warming to room temperature for one hour. The reaction was quenched by the addition of 20 mL of water and sufficient acetic acid to neutralize the mixture. The reaction mixture was extracted with ethyl acetate (3xc3x9730 mL), and the combined organic extracts were extracted with 1N NaOH solution (4xc3x9715 mL). The combined aqueous extracts were acidified with acetic acid and extracted with EtOAc (3xc3x9720 mL). The organic phase was washed with brine, dried over anhydrous MgSO4, filtered and concentrated in vacuo to give 2-methoxy-6-dimethylamino-phenylboronic acid.
Step B
N-(CBZ)-(L)-4-(2xe2x80x2-methoxy-6xe2x80x2-dimethylamino-phenyl)-phenylalanine, tert-butyl ester.
2-Methoxy-6-dimethylamino-phenylboronic acid (0.18 g, 0.9 mmol), N-(CBZ)-(L)-4-(trifluomethylsulfonyloxy)-phenylalanine tert-butyl ester (0.36 g, 0.73 mmol), potassium carbonate (0.37 g, 2.7 mmol) and 15 mg of tetrakistriphenylphospine palladium(0) were suspended in 2 mL of toluene and 1 mL of ethanol. The mixture was heated at 90xc2x0 C. for 3 hours, diluted with ethyl acetate, washed with water, dried over anhydrous MgSO4, filtered and concentrated in vacuo. The residue was purified by MPLC on silica gel eluted with a gradient of 10-90% EtOAc in hexanes to provide N-(CBZ)-(L)-4-[(2xe2x80x2-methoxy-6xe2x80x2-dimethylamino)phenyl]phenylalanine, tert-butyl ester as a colorless oil.
NMR (400 MHz, CDCl3): 1.41 (d, 9H); 2.45 (s, 6H); 2.45 (s, 6H); 3.15 (d, 2H); 3.70 (s, 3H); 4.60 (m, 1h); 5.15 (m, 2H); 5.40 (bd, 1H); 5.65 (d, 1H); 5.72 (d, 1H); 7.18-7.40 (m, 10H).
Step C
(L) 4-[(2xe2x80x2-methoxy-6xe2x80x2-dimethylamino)phenyl]phenylalanine, tert-butyl ester.
N-(CBZ)-(L)-4-[(2xe2x80x2-methoxy-6xe2x80x2-dimethylamino)phenyl]phenylalanine, tert-butyl ester was hydrogenolyzed as described in Reference Example 9 Step B to give the title compound. NMR (400 MHz, CDCl3): 1.42 (s, 9H); 2.45 (s, 6H); 2.87 (m, 1H); 3.06 (m, 1H); 3.65 (m, 1H); 3.70 (s, 3H); 6.65 (d, 1H); 6.72 (d, 1H); 7.20-7.38 (m, 6H).
The product of Reference Example 8, Step D, N-(CBZ)-(L)-4-[(2xe2x80x2-methoxy-6xe2x80x2-hydroxy)phenyl]phenylalanine, tert-butyl ester was hydrogenolyzed as described in Reference Example 9, Step B to give (L)-4-[(2xe2x80x2-methoxy-6xe2x80x2-hydroxy)-phenyl]phenylalanine, tert-butyl ester.
1H-NMR (400 MHz, CDCl3):1.44 (s, 9H); 2.88 and 3.05 (dAB, 2H); 3.62 (m, 1H); 3.72 (s, 3H); 6.55 9d, 1H); 6.65 (d, 1H); 7.20 (t, 1H); 7.32 (m, 4H).
Step A
N-(BOC)-(L)-4-(2xe2x80x2,6xe2x80x2-dichlorobenzamido)phenylalanine, methyl ester.
N(a)-(BOC)-(L)-4-(FMOC-amino)-phenylalanine, methyl ester (9.62 g, 18.6 mmol) was dissolved in 15 mL of DMF and treated with diethylamine(11.6 mL, 112 mmol). The reaction mixture was stirred at room temperature for two hours, then concentrated in vacuo to give an viscous oil. This residue was dissolved in CH2Cl2 (50 mL) then treated with diisopropylethylamine (5.16 mL, 27.9 mmol) and 2,6-dichlorobenzoyl chloride (2.93 mL, 20.4 mmol). The reaction mixture was stirred overnight at room temperature and then quenched with H2O (40 mL). The layers were separated and the aqueous layer was extracted with CH2Cl2 (2xc3x9740 mL). The organic layers were combined and washed with brine (1xc3x97200 mL) then dried over anhydrous MgSO4. The mixture was filtered and concentrated in vacuo, then the residue was purified by flash column chromatography eluted with 50% EtOAc in hexane to give N-(BOC)-(L)-4-(2xe2x80x2,6xe2x80x2-dichlorobenzamido)phenylalanine, methyl ester (7.3 g).
500 MHz 1H NMR (CDCl3): 1.44 (s, 9H); 3.12 (m, 2H); 3.75 (s, 3H); 4.61 (m, 1H); 5.00 (d, 1H); 7.15 (d, 2H); 7.32 (m, 3H); 7.59 (d, 2H).
Step B
(L)-4-(2xe2x80x2,6xe2x80x2-dichlorobenzamido)phenylalanine, methyl ester hydrochloride.
N-(BOC)- (L)-4-(2xe2x80x2,6xe2x80x2-dichlorobenzamido)phenylalanine, methyl ester (2.50 g, 5.35 mmol) was dissolved in dioxane (5 mL) and treated with HCl in EtOAc (18.4 mL of 2.9 N). The mixture was stirred overnight at room temperature, then concentrated in vacuo to give a quantitative yield of (L)-4-(2xe2x80x2,6xe2x80x2-dichlorobenzamido)-phenylalanine, methyl ester hydrochloride.
500 MHz 1H NMR (CD3OD): 3.17 (m, 1H); 3.28 (m, 1H); 3.84 (s, 3H); 4.33 (m, 1H); 7.28 (d, 2H); 7.46 (m, 3H); 7.68 (d, 2H).
Step A
N-(BOC)-(D,L)-Nipecotic acid, ethyl ester
To a solution of (D,L)-nipecotic acid, ethyl ester (Aldrich Chemical, 10 g, 63.6 mmol) in methylene chloride (50 mL) was added portionwise di-tert-butyl dicarbonate (13.9 g, 63.7 mmol). After stirring at room temperature for two hours, the solvent was removed under reduced pressure, and the residue was used directly in the subsequent step.
Step B
N-(BOC)-(D,L)-3-Phenylthio-nipecotic acid, ethyl ester
To a solution of potassium hexamethyldisilazide (46 mL, 0.5M in THF, 23 mmol) in THF (120 mL) at xe2x88x9278xc2x0 C., was added a solution of N-(BOC)-(D,L)-nipecotic acid, ethyl ester (6 g, 23 mmol) in 30 mL of THF. After stirring at this temperature for 35 min, diphenyl disulfide (5.5 g, in 10 mL THF) was added dropwise. After 5 min, the mixture was allowed to warm to ambient temperature. The mixture was poured into saturated ammonium chloride solution (200 mL) and extracted with ethyl acetate (300 mL). After drying the organics over anhydrous magnesium sulfate and filtration, the solvent was removed under reduced pressure. The resulting residue was purified by flash column chromatography on silica gel eluted with 8% EtOAc in hexanes giving N-(BOC)-(D,L)-3-phenylthio-nipecotic acid, ethyl ester (9.7 g).
Step C
N-(BOC)-(D,L)-3-Phenylthio-nipecotic acid.
To a solution of 8.8 g (22 mmol) of N-(BOC)-(D,L)-3-phenylthio-nipecotic acid, ethyl ester in 75 mL of ethanol and 50 mL of water was added 2.2 g (55 mmol) of NaOH. The solution was heated at 80xc2x0 C. for 3 hours and then at 50xc2x0 C. overnight. The solution was diluted with 100 mL of water and extracted with ethyl acetate (3xc3x9750 mL). The aqueous phase was acidified with HCl and extracted with ethyl acetate (3xc3x9775 mL). The combined organic phases were washed with brine and dried over anhydrous MgSO4, filtered and concentrated in vacuo to give N-(BOC)-(D,L)-3-phenylthio-nipecotic acid.
Step D
N-(BOC)-(D,L)-3-Phenylsulfonyl-nipecotic acid.
To a solution of 6.9 g of N-(BOC)-(D,L)-3-phenylthio-nipecotic acid in 100 mL of acetic acid was added at 0xc2x0 C. 32 mL of 30% hydrogen peroxide solution. The reaction mixture was allowed to gradually warm to room temperature. The progress of the reaction was monitored by HPLC. After stirring overnight, the reaction mixture was cooled in an ice bath and was treated with a saturated solution of Na2SO3 until KI/starch paper indicated that the hydrogen peroxide had been consumed. The pH was confirmed as 5.0 and the solution was extracted with ethyl acetate (4xc3x9775 mL). The combined organic phases were washed with brine and dried over anhydrous MgSO4, filtered and concentrated in vacuo to give N-(BOC)-(D,L)-3-phenylsulfonyl-nipecotic acid, which crystallized upon standing.
400 MHz 1H NMR (CD3OD); xcex4 1.59 (s, 9H); 1.65-1.75 (m, 2H); 1.79 (m, 1H); 2.06 (dt, 1H); 2.40 (bd, 1H); 2.75 (bs, 1H); 3.85 (bd, 1H); 4.65 (d, 1H); 7.62 (t, 1H); 7.75 (t, 1H); 7.86 (d, 1H).
General Method 1: Amino acid coupling conditions.
In general, 1.0 eq of amino acid ester was coupled to 1.5 eq of (3-sulfonyl or sulfenyl)-N-(BOC)-cyclic amino acid by reaction in DMF with 1.5 eq HOBt or HOAt, 1.5 eq of HBTU or HATU followed by 4.5 eq of diisopropylethylamine. After stirring overnight, under nitrogen, the reaction mixture was diluted with ether or ethyl acetate and was washed with 1N HCl (2xc3x97), saturated NaHCO3 (2xc3x97), and brine (1xc3x97) and was dried over anhydrous MgSO4. The reaction mixture was filtered and concentrated in vacuo and the residue was purified on silica gel eluted with ether/hexanes or ethyl acetate/hexanes mixtures to recover the desired product.